The invention described herein is a pipeline pig that provides a method of applying a treating fluid, such as an inhibitor, within a pipeline to specific longitudinal areas along the inner wall of the pipeline and particularly to the upper interior portions of the interior wall of a pipeline.
Pipelines, particularly those designed to carry large volumes of gas under pressure, are customarily made of metal and usually of steel; Steel is the preferred metal for construction of a pipeline due to its inherent strength, availability and economy. However, steel is subject to corrosion as a consequence of oxidation or reaction with gasses or liquids, such as water, that is commonly encountered when large volumes of gas are delivered through a pipeline. To combat corrosion a standard technique employed by many operators of pipelines is to periodically deposit inhibitor liquid within the pipeline. The liquid can be moved by the flow of gas through the pipeline or more commonly, by the use of pipeline pigs inserted into the pipeline that are moved by the flow of gas, the pigs serving to provide a moving plunger within the pipeline that tends to sweep liquid within the pipeline before it and to therefore move the liquid through the full length of the pipeline.
One method of applying a treating liquid to the interior of a pipeline is called “batching” in which treating liquid is captured between two pipeline pigs that move in tandem through a pipeline pig with the treating liquid therebetween. Although this method is widely accepted and used it does not insure that the upper quadrant of the interior of a pipeline is adequately coated with or exposed to the treating liquid.
A second method of treating the interior cylindrical surface of a pipeline is called the “injection method.” In this method, the treating liquid is injected directly into the pipeline and is moved by gas flow to carry the liquid through the length of the pipeline. This method is costly and usually requires that treating liquids be more or less continuously injected into the pipeline. There is no direct application, in this method, of the treating liquid to the inner wall since liquid simply rests on the bottom interior surface of the pipeline as it moves along the length of the pipeline.
To combat these problems, the pipeline pig of this invention provides a method of distributing liquid present in the lower portion of a pipeline to the interior upper quadrant of the pipeline interior as the pig passes by the flow of gas through the length of the pipeline.
For background information relating to pipeline pigs that have similar uses and applications reference may be had to the following previously issued United States patents and a U.S. patent application publication:
U.S. Pat. No.Inventor(s)Title2,707,934CurtisPipeline Treating Plug3,111,431WeaverInterior Pipe Coating Device3,643,280PowersPipeline Pigs4,411,039Timmins, et al.Removal of Condensed Gas fromthe Walls of Gas Pipelines4,774,905NobisApparatus for InternallyCoating Pipes5,795,402Hargett, Sr. et al.Apparatus and Method forRemoval of Paraffin Depositsin Pipeline Systems6,138,697Horger, et al.Hydrodynamic Apparatus forCleaning Channels and forMonitoring Channels6,263,534McCann, et al.Delivery DeviceUS2001/0017147GazewoodMethod for Jetting a Fluid